The present invention relates in general to a method for estimating the propensity of a vehicle to rollover, and more specifically, to a method for detecting an approach to a rollover event of a vehicle and providing a corrective action to reduce the likelihood of an actual rollover.
Dynamic stability control systems have been implemented in vehicles to deter a vehicle from actually rolling over. Vehicle rollovers have become a growing concern for vehicles with a high center of gravity and especially those used for multiple purposes in different geographical locations. A vehicle may have the potential to rollover due to forces exerted on the vehicle under different types of operating conditions. Methods have been used to anticipate when the vehicle has the propensity to rollover and to make adjustments to counteract vehicles having that propensity from rolling over.
A rollover event, as used in this application, is defined as a moment when current vehicle operating conditions (e.g., speed, steering angle, lateral acceleration, etc.) approach a threshold where the rollover could actually occur. Typically, stability control systems detect or estimate the propensity for a rollover event to occur by measuring a roll angle or a roll rate. This requires a dedicated sensor for determining the roll angle at each instance the vehicle is in travel. Sensors are costly and require dedicated wiring and packaging locations. Vehicle manufacturers are consistently looking for reliable methods which can obtain the same results yet cost less and minimize the number of components on the vehicle.
It is also known to use differential braking to induce understeer and limit lateral acceleration. Such methods include electronic stability control and active roll management. These systems typically detect critical lateral acceleration, wheel lift detection, vehicle roll rate (roll angle), and roll energy. Suspension based systems use active roll control and active damper controls. Steering based systems typically use active front steer (steering angle overlay) and four wheel steering (active rear steer) to control tire lift from occurring. Each of these methods typically use vehicle inertial based sensors.
Another method for detecting a rollover event of a vehicle and providing a corrective action to reduce the likelihood of an actual rollover is described in pending U.S. patent application Ser. No. 10/719,968 filed Nov. 21, 2003 (hereinafter referred to as the '968 application), the disclosures of which are incorporated herein by reference. The invention disclosed provides a method for detecting a rollover event of a vehicle and providing a corrective action to counteract an actual rollover by using lateral kinetic energy and lateral acceleration of the vehicle to detect the rollover propensity. In one aspect of the invention, a method is provided for detecting a rollover propensity of a vehicle. A lateral kinetic energy of the vehicle is determined in response to vehicle longitudinal velocity and vehicle side slip angle. A lateral acceleration of the vehicle is then measured. A rollover potentiality index is determined in response to the lateral kinetic energy and the lateral acceleration. A rollover index is determined by weighting the rollover potentiality index by a factor of the lateral acceleration. A comparison is made to determine if the rollover index is above a predetermined threshold.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in-light of the accompanying drawings.